Along with Samsung's release of the 840 Pro SSD today, Samsung is also releasing a more mainstream oriented 840 SSD. It's based around the same Samsung MDX controller as the Pro series, but uses 3-bit-per-cell (TLC) NAND instead of 2-bit-per-cell (MLC) NAND found in the 840 Pro. The 840 Pro also has a firmware which is tuned for heavier workloads consisting of more writes and random IOs, whereas the 840 is designed more towards read centric (i.e. consumer) workloads.

Samsung SSD 840 Pro vs 840 vs 830

Samsung SSD 830 (256,512GB)

Samsung SSD 840 (500GB)

Samsung SSD 840 Pro (256,512GB)

Controller

Samsung MCX

Samsung MDX

Samsung MDX

NAND

27nm Toggle-Mode 1.1 MLC

21nm Toggle-Mode 2.0 TLC

21nm Toggle-Mode MLC

Sequential Read

520MB/s

540MB/s

540MB/s

Sequential Write

400MB/s

330MB/s

450MB/s

Random Read

80K IOPS

98K IOPS

100K IOPS

Random Write

36K IOPS

70K IOPS

78K IOPS

Samsung is actually the first manufacturer to publicly release a TLC NAND based SSD, so we will have very interesting time testing it. Remember, adding more bits per cell reduces endurance and also increases program, erase and read latencies. In a Q&A session Samsung couldn't tell us any exact P/E cycle numbers, but they claimed that the 840 has higher endurance than many competitors MLC based SSDs. We didn't get more specifics than that, but we hope to be able to test this as soon as possible. As for the performance, Samsung again wouldn't tell us any raw latency numbers, but they said their TLC NAND is roughly 50% slower than their MLC NAND. For a more in-depth look at the architectural differences between MLC and TLC, refer to our Understanding TLC NAND article.

Samsung SSD 840 Series Pricing

64GB

128GB

256GB

512GB

Samsung SSD 840

N/A

$109.99 (120GB)

$199.99 (250GB)

$449.99 (500GB)

Samsung SSD 840 Pro

$99.99

$149.99

$269.99

$599.99

The regular 840 SSD will be available in capacities of 120GB, 250GB and 500GB. The increased amount of spare area makes sense given the use of lower endurance TLC NAND. The 840 will be available as a bare drive or in a notebook kit, which adds $20 to the prices in the table. Both, the 840 and 840 Pro will be available on October 15th.

Samsung only provided 256GB 840 Pro SSDs for reviews, so unfortunately we haven't been able to test the 840 yet. However, I should get our review sample later today and hopefully some other capacities of the 840 Pro as well.

TLC does follow the same 2^n math because the die is cut down in size. So an 8GB MLC die has 4 billion cells (actually more since NAND size is actually measured in Gibibytes) but with TLC that number is reduced to ~2.67 billion cells (multiply that by three and you get ~8GB). The die is physically smaller, which leads to more dies per wafer and hence cost savings.

Well my point was that 8GiB has exactly 2^n bits, which is not divisible by 3, so you can't even reach exactly 8GiB with TLC unless you treat the last transistor as SLC (8, 32 GiB) or 2bpc MLC (16 GiB).So maybe they skipped the whole 2^n thing and went with something that adds up to approx. 120GB total.Anyway, more spare area makes more sense, I was just thinking out loud.Reply